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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 1 |
| 3 | 4 |
| 4 | 12 |
| 5 | 90 |
| 6 | 1425 |
| 7 | 136135 |
| 8 | 195100084 |
| 9 | 26562489095540 |
| 10 | 5182344411607842435270 |
| 11 | 137655966922842171797061456838751550 |
| 12 | 713380630907065135419001299147560152192298801082595247675 |
[1,1,4,12,90,1425,136135,195100084,26562489095540, 5182344411607842435270, 137655966922842171797061456838751550, 71338063090706513541900129914756015219229880108259\ 5247675] |